Video productions involve a variety of different camera shots and angles. For example, news programs might variously require shots of the whole news set, or the anchors, or side shots for sports or weather. The variety and rapidity of the shots necessitate having several cameras. Historically, each camera was mounted to a manually-operated camera dolly. Each dolly would have an operator, who would set up shots according to short instructions received from the director, such as “camera 2, weatherman”. The operator would manually push the dolly around, steering it by turning a horizontal steering wheel that surrounded its column. The steering wheel turned all three of the dolly's wheels in unison, always pointing them in the same direction. This allowed the dolly to be moved about on the studio floor using a “crab” motion, in which the rotational orientation of the dolly remained unchanged. This configuration allowed for very smooth on-air moves, especially when the camera needed to be kept pointing in the same direction.
While this model has worked for decades, nonetheless it is very labor intensive, and as a consequence, studios are increasingly exploring the use of robotic camera dollies. Robotic dollies become especially appropriate for news and other productions where the shots are repetitive from one show to the next. As such, the shots can be set up ahead of time, named, and then recalled during the production by the director's pressing a button, without the need for camera operators.
One robotic camera dolly manufactured by Radamec Incorporated uses an architecture in which servomechanisms are added to dollies that are otherwise essentially manual dollies. That is, the robotic versions substitute a first servomechanism for the steering wheel of a conventional dolly, and substitute a second servomechanism for the operator pushing the conventional dolly. To provide the balanced motive force equivalent to the operator pushing the conventional dolly, a robotic dolly has three driven wheels, as otherwise the dolly will have a tendency to travel in an arc. However, achieving this balance complicates the steering and drive mechanisms, since whatever motive force propels the wheels must now be coupled through whatever steers the wheels. Such coupling is further complicated by the necessity that the wheels must be able to swivel in a full circle. Since the preferred method of navigation is by dead reckoning, that is calculating the position of the dolly by integrating its increments of distances traveled, its ultimate navigational accuracy will be limited by how precisely the dolly can be kept in alignment.
The consequence of small misalignments is that over a period of minutes, such dollies will slowly lose their rotational orientation. Such errors are problematic, since, with their wheels not being able to point in different directions, such dollies have no way to reorient themselves. The only remedy is for an operator to intervene, disconnect the robotics, and manually reorient the dollies.
A different robotic dolly configuration manufactured by Total Spectrum Manufacturing and Vinten Broadcast Limited and disclosed in U.S. Pat. Nos. 5,153,833, 5,008,804, and 4,959,798 overcomes the limitation just described by providing for independent steering of each of its three wheels. Like the Radamec dollies, these dollies also accumulate rotational errors. However, because these dollies are provided with means for independently steering each of their wheels, they are able to steer their wheels into a circle, and drive them sufficiently to rotate the dollies back into their nominal rotational orientation. While by itself this capability is an advantage, the action of swiveling the wheels back and forth against the floor at the same time causes the dolly to move slightly and in an unrepeatable manner. Thus, correcting one error creates yet another error. Further, independent steering makes the wheel mechanisms more complicated. Each wheel mechanism now requires a set of electrical slip rings, an independent steering motor with its own electronics, and an independent drive motor, also with its own electronics.
In summary, television and film studios welcome robotics to the extent that they can reduce costs, reduce absentee problems, and let them offer camera operators more stimulating jobs in the studio. While the best of the present robotic camera dollies perform reasonably well, their complexity makes them overly expensive for widespread adoption. Despite being thirteen years since their first introduction, such dollies manufactured today have done little more than motorize the mechanisms of the older mechanical configurations. A search of the literature, together with a familiarity with the industry, have failed to uncover any art representing an improvement over these complicated designs.